
Solar filament/prominence eruptions:
A Solar filament is a large current system lie above the magnetic polarity inversion line (PIL) ([1]}, [2]}). These structures contain dense and cool (\(\approx \)  10\(^4\)  K) plasma against the hot corona and appear as dark thread like structures, when observed on the solar disk. Beyond the solar limb, these structures are termed as prominences and appear as bright cloud like features. So the filaments and prominences are identical structures observed in different locations i.e. on solar disk or solar limb respectively. They are observed in the chromosphere (H\(_\alpha \) ) or in the lower corona (EUV observations). Filaments formed at the chromospheric height are usually associated with fibrils along the PIL and called spicules when observed over the limb ([3]}, [4]}). An EUV observation of solar prominence with SDO/AIA in two wavelengths (304 Å, and 171 Å) is presented in Figure REF . [5]} clarified that the body of the filament consists of three main structural components, namely (a) spine, (b) barbs, and (c) extreme ends. The long horizontal part of the filament is called the spine, and it forms the main filament structure. From the sides of the spine, there are small branches protrude with an acute angle with respect to the main body. These small branches are called barbs and provide a support to the filament system ([6]}).
The beginning and end points of the spine are the two extreme ends of the filament. These filament structures are shown in Figure REF , where the huge filament lies on the solar disk observed on March 14, 2015. Filaments are observed in quite as well as ARs and well studied by many authors ([7]}; [8]}; [9]}; [10]}; [11]}).
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Solar flares:
Solar flares are seen as the bright flashes on the Sun. It is defined as a brightening of any emission observed across the electromagnetic spectra with a lifetime of minutes ([12]}). The first observation of solar flare was observed in the continuum of white light by R. C. Carrington and R. Hodgson in 1859, afterwards flares are being observed and modelled by many authors ([13]}; [14]}; [15]}; [16]}; [17]}; [18]}; [19]}; [20]}; [21]}). Usually flares occur in the ARs with a complex geometry of 3D magnetic field ([22]}; [23]}). The different phases of a flare eruption are presented in Figure REF .
The plasma in the base of the flare region starts to heat up in the preflare phase and appear in the soft X-rays and EUV.
Electrons and ions are accelerated for the impulsive phase and release an enormous amount of energy. At the chromosphere, hard X–ray footpoints are visible at this phase ([24]}). In the radio band, some of the particles with high energy are kidnapped, and as a result of that intensive emission is being produced. Energy is distributed in decimetre's pulsations in the impulsive phase, where soft X–rays and H\(_\alpha \)  emissions show a maximum intensity.
H\(_\alpha \)  intensity shows a rapid increase in the flash phase.
According to Geostationary Operational Environmental Satellite (GOES) and National Oceanic and Atmospheric Administration (NOAA) flaring classification to their X–ray brightening between 1–8 Å range, flares are classified as three main categories, namely: C, M, and X class flares (there are two more classes A and B, for the weaker eruptions).
In this tenfold classification each class is 10 times more powerful than the previous one. So an X class flare is 10 times stronger than an M class flare and 100 times more powerful than a C class flare. Each category of flare class has further nine subdivisions from C1 to C9, M1 to M9, and X1 to X9 (for the X class the sub classification goes higher and higher upto X28).
Solar flares are usually accompanied by an emission of high energy particles, with energy release upto 100 MeV. In October 2003, a flare of X28 class was observed and remains as the most strongest flare eruption till now and produced big Halloween storms ([25]}). Recently in September 2017, many X and M class flares were produced and contributed in the large geomagnetic storms, which are responsible for the space-weather phenomenon. An example of solar flare observed in multi-wavelength EUV filters with SDO/AIA on the eastern limb on March 9, 2011 is presented in Figure REF .
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Coronal Mass Ejections (CMEs):
CMEs are the largest scale spectacular eruptions from the solar atmosphere. It appears as an outward motion of a big, bright, and detached white light feature in the coronagraph ([26]}; [27]}; [28]}). In the eruption process, a huge mass of plasma (\(\approx \)  10\(^{11}\) -10\(^{13}\)  kg) is tugged out towards the interplanetary space with speed of 100 km s\(^{-1}\)  to more than 1000 km s\(^{-1}\)  ([29]}). In this journey they may interact frequently with the Earth and impacts the terrestrial environment and other high-tech systems in various ways ([30]}; [31]}).
Observational studies indicate that CMEs can be observed in many wavebands i.e., soft X-rays ([32]}; [33]}), optical and EUV ([34]}), and in radio ([35]}).
During a CME, radio-frequency observations provide first indication of large-scale structural change of the solar corona. They reveal if the energetic electrons are kidnapped in the large coronal structures or moving within the open magnetic field lines. Observations of type II radio bursts associated with CMEs tells about the propagation of MHD shock waves. The signatures of type III radio bursts with CME show that open magnetic fields can generate in the ARs as well as in the coronal holes ([28]}).
The CME occurrence rate, with an identification by eye, is available at http://cdaw.gsfc.nasa.gov/CME_list ([37]}). This catalogue shows that the rate of CME occurrence increases from \(\approx \)  0.5/day near solar minimum to \(\approx \)  6/day near solar maximum ([38]}; [29]}).
By the appearance, CMEs can be classified as the narrow CMEs and normal CMEs. Narrow CMEs look like a jet moving along the open magnetic field lines, whereas the normal CMEs contain a three part structure as shown in Figure REF . In this structure, a bright front loop is followed by a dark cavity, which again is embedded with a bright core ([40]}).
Often, CMEs are accompanied by solar flares and both are considered to be a signature of same magnetic event. Filaments and some times other small scale eruptions, i.e. solar jets, also follow a CME eruption towards the interplanetary medium ([37]}; [11]}).
These large scale eruptions are well explained with CSHKP model proposed by [43]}, [44]}, [45]}, [46]} and further extended for 3D by [47]}, [48]}. CSHKP model explained the flare ribbon formation, their separation, and dynamical flare kernels. To explain the triggering mechanism of solar eruptions, three models were further proposed, namely tether cutting model, magnetic breakout model, and kink instability model. All these models are based on the instability of the flux rope which results as the loss of equilibrium. For tether cutting mechanism, the magnetic reconnection occurs below the erupting filament while for breakout it occurs high in the corona in null points. Kink instability comes into account where the twist comes in picture and reaches to a critical value.

